Enhancement of green terbium-related photoluminescence from highly doped microporous alumina xerogels in mesoporous anodic alumina

Strong enhancement of green photoluminescence (PL) from microporous alumina xerogels, highly doped with terbium (from 30 to 60 wt % as Tb2O3), is reported. The regular structure of a 30 mm thick, mesoporous anodic alumina layer was exploited for spin-on deposition of the alumina xerogel in a single step. The green PL, associated with predominant D-5(4) --> F-7(5) transitions, along with D-5(4) --> F-7(j), j = 3, 4, 5, 6 transitions of Tb3+, was found to increase with terbium concentration in the alumina xerogel. This effect is attributed to cross-relaxation. The thermal quenching of the green terbium-related emission does not exceed a factor of two within a temperature range from 10 to 300 K for any of the alumina xerogels confined in anodic alumina. Further, such quenching is much reduced with the rise of temperature compared with (i) Tb-doped titania xerogel, (ii) Tb-implanted thermally grown silicon dioxide film, and (iii) Tb-doped alumina xerogels fabricated onto monocrystalline silicon. Thus, the terbium-doped structure comprising alumina xerogel/anodic alumina is proposed as a basis for green room-temperature luminescent images. (C) 2001 The Electrochemical Society.